Hi mate.
Is it yours or councils?
I ask as if it's yours you can be quite creative with protecting it.
Those guards are good, but only as good as the ground you set them into. There's also a school of thought that suggests that if you have a good shiny new lock, they'll be drawn to the garage "Because you must have something worth protecting". I would strongly suggest painting it a really drab colour to help it blend it, or at least look inconspicuous.
You can get cheap alarms these days, but if you have pics of how they tried to get in, that would help me suggest something more useful.
If the door and the frames are GOOD, these take some beating
http://www.ebay.co.uk/itm/ENFIELD-GENUI ... 407wt_1270
Mounted nice and low if it's an up and over door.
I've built booby traps before, sorry, I mean pointed out potential hazards for burglars before to worried owners, but you need to be very careful and it MUST be privately owned.
Don't hesitate to give me a shout if you need anything more.